Method and apparatus for sector channelization and polarization for reduced interference in wireless networks

ABSTRACT

The present invention provides in one embodiment channel allocation and polarization techniques for reducing cross sector communications interference in a multiple access wireless communications environment. In one embodiment, channel allocation and/or polarization techniques may be applied in multiple-access wireless communications architectures to provide selective, simultaneous communications with wireless devices using a plurality of transmitters. In some embodiments, a transmitter is coupled to an antenna configured to provide simultaneous communications with wireless devices located in different spatial areas or sectors. In some embodiments, communications between wireless devices within a single sector, between wireless devices in different sectors and between wireless devices and a wired network or wireless backhaul network may be provided.

RELATED APPLICATIONS AND CLAIM OF PRIORITY

The application is a Divisional of U.S. Non-provisional patentapplication Ser. No. 10/858,936 entitled “Method and Apparatus ForSector Channelization And Polarization For Reduced Interference InWireless Networks,” filed Feb. 8, 2006, which claims the benefit of aU.S. Provisional Patent Application No. 60/492,017 entitled, “WirelessCommunication Architecture,” filed Aug. 1, 2003, the contents of whichare incorporated herein by reference in its entirety for all purposes.

This application is related to U.S. Non-provisional patent applicationSer. No. 10/615,208, entitled, “Multiple Access Wireless CommunicationsArchitecture,” filed Jul. 7, 2003 and subsequently issued on Jul. 24,2007 as U.S. Pat. No. 7,248,877 B2, which claims priority from U.S.Provisional Patent Application No. 60/428,456, entitled “Approach ForUsing Spatial Division To Increase Throughput In A WirelessCommunications System,” filed Nov. 21, 2002, the contents of which areincorporated herein by reference in its entirety for all purposes.

FIELD OF THE INVENTION

This invention relates generally to wireless communications systems and,more specifically, to selection of number of sectors, channel allocationand polarization techniques for reducing interference and increasingnetwork performance in a wireless communications architecture.

BACKGROUND OF THE INVENTION

The approaches described in this section are approaches that could bepursued, but not necessarily approaches that have been previouslyconceived or pursued. Therefore, unless otherwise indicated, theapproaches described in this section may not be prior art to the claimsin this application and are not admitted to be prior art by inclusion inthis section.

A communications network is any system or mechanism that provides forthe exchange of information or data between participants. In existingwireless communications networks, such as a wireless Local Area Networks(LANs) or Personal Area Networks (PANs), a wireless access pointfunctions as a transceiver in communicating with a number of wirelessdevices. As used herein, the term “wireless device” refers to any typeof device that uses a wireless communications protocol to communicate.Example wireless devices include, without limitation, desktop, laptopand handheld computers, Personal Digital Assistants (PDAs), cell phonesand various other portable devices. The radiation pattern of wirelessaccess points is usually omni directional, i.e., the wireless accesspoint transmits information in 360 degrees, so that all wireless deviceswithin range of the wireless access points receive all transmittedsignals. Wireless access points also perform various managementfunctions, such as selecting specific frequencies on which to transmitdata to particular wireless devices in the system.

One ongoing issue with wireless communications architectures is how toincrease the number of wireless devices that can simultaneouslycommunicate within a specified physical area given a fixed amount ofallocated electromagnetic spectrum. This is particularly important whena number of wireless devices in the specified area are attempting tosimultaneously communicate with a wireless access point to access acommunications network, such as the Internet. For example, it is notuncommon for large numbers of users to use laptop computers to accessthe Internet during tradeshows and conferences. As another example, insome corporate offices, many users share wireless access points toaccess the Internet with laptop computers. As yet another example, manycoffee shops now offer free wireless Internet access to customers. Allof these situations strain the available access resources since only alimited number of available communications channels must be shared byall participants. For example, the IEEE 802.11(b)/(g) standard in theFCC regulatory domain, sometimes referred to as “WiFi”, defines 11communications channels. Thus, assuming that each channel is dedicatedto a single user, only 11 users can communicate simultaneously.

Conventional approaches for addressing this problem include employingmultiple access communications protocols to increase the number ofwireless devices that can simultaneously access a wireless access point.Example multiple access communications protocols include, withoutlimitations, Frequency Division Multiple Access (FDMA), Time DivisionMultiple Access (TDMA), Code Division Multiple Access (CDMA) and CarrierSense Multiple Access (CSMA). The use of multiple access communicationsprotocols can significantly increase the number of wireless devices thatcan operate simultaneously on a specified set of communicationschannels. For example, the use of TDMA can triple the number of wirelessdevices that can share a specified set of communications channelscompared to FDMA. Even using TDMA however, a wireless access point cancommunicate to only one wireless device in any one timeslot. Furthermorefor any wireless device to communicate to another wireless device or tothe wired network, it must transmit its data to the wireless accesspoint. The wireless access point then transmits the data to anotherwireless device or to the wired infrastructure, such as the Internet.The throughput of the network is therefore necessarily limited by thethroughput of communications between the wireless access point and anyone wireless device at a particular point in time. Consequently, inexisting systems, the amount of data that can be transferred at any onetimeslot is equal to the throughput of the link from the wireless accesspoint to the particular wireless device to which it is communicating.All other wireless devices are in a state waiting for a free time slotto transmit or receive a quantum of data.

Cross-channel interference is another issue confronting conventionalapproaches. In the previously described example of the IEEE 802.11(b)standard in the FCC regulatory domain, the 11 communications channelsoften overlap one another. Thus, assuming that two users are each usingdifferent but overlapping channels, the two users' communications couldinterfere with one another.

Management and growing of networks of Wireless Access Points is acomplicated process. Adding another wireless access point generallyrequires one to adjust the power and channel assignments of accesspoints in the vicinity of a new access point in order to avoidinterference.

Based on the foregoing, there is a need for a wireless communicationsarchitecture that does not suffer from limitations in prior approaches.There is a particular need for a wireless communications architecturethat allows a greater number of wireless devices to communicatesubstantially simultaneously with little or no interference.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements and in which:

FIGS. 1A-1G are functional diagrams of a wireless communicationsapparatus configured in accordance with an embodiment of the invention.

FIG. 2 is a block diagram that depicts a wireless communicationsapparatus configured in accordance with an embodiment of the invention.

FIG. 3A is a block diagram that depicts a wireless communicationsarchitecture configured in accordance with an embodiment of theinvention.

FIG. 3B is a block diagram that depicts a wireless communicationsarchitecture configured in accordance with an embodiment of theinvention.

FIG. 4A is a functional diagram that depicts a plurality of frequencychannels according to the 802.11b standard in an embodiment of theinvention.

FIG. 4B is a functional diagram that depicts one set of three channelschosen from the channels illustrated by FIG. 4A.

FIG. 5 is a functional diagram that depicts an example of an antennaradiation pattern in an embodiment of the invention.

FIGS. 6A-6D are flowcharts depicting channel allocation processing inaccordance with an embodiment of the invention.

FIG. 7 is a functional diagram that depicts variations of an examplesector-ordered 6-channel set in accordance with an embodiment of theinvention.

FIG. 8 is a functional diagram that depicts polarization assignment inan embodiment of the invention.

FIG. 9 is a functional diagram that depicts another examplecross-polarization assignment in accordance with an embodiment of theinvention.

FIG. 10A is a block diagram that depicts a top view of an antennaapparatus configured in accordance with an embodiment of the invention.

FIG. 10B is a side view of the antenna apparatus of FIG. 10A.

FIG. 11A is a block diagram of an end view of a radiating assemblyconfigured in accordance with an embodiment of the invention.

FIG. 11B is a block diagram that depicts a patch element configuredaccording to an embodiment of the invention.

FIG. 12 is a block diagram that depicts a computer system on whichembodiments of the invention may be implemented.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be apparent, however, toone skilled in the art that the present invention may be practicedwithout these specific details. In other instances, well-knownstructures and devices are shown in block diagram form in order to avoidunnecessarily obscuring the present invention. In some instances, flowdiagrams are used to depict steps performed in various embodiments ofthe invention. The invention is not limited to the particular order ofsteps depicted in the figures and the order may vary, depending upon therequirements of a particular implementation. Furthermore, steps that aredepicted and described may be removed and/or other steps may be added,depending upon the requirements of a particular implementation. Variousaspects of the invention are described hereinafter in the followingsections:

-   -   I. OVERVIEW    -   II. OPERATIONAL OVERVIEW    -   III. WIRELESS COMMUNICATIONS APPARATUS    -   IV. COMMUNICATIONS CHANNELS, PROTOCOLS AND MULTIPLE ACCESS        SCHEMES    -   V. INTERFERENCE MITIGATION AND POWER CONTROL    -   VI. ANTENNA CONFIGURATIONS    -   VII. IMPLEMENTATION MECHANISMS, ALTERNATIVES & EXTENSIONS

I. Overview

As described in this disclosure, in one embodiment, a sectorized accesspoint with the capability to tailors its configuration can provide theability to reduce network disruption and to also increase networkperformance.

The present invention provides in one embodiment channel allocation andpolarization techniques for reducing interference in a wirelesscommunications environment. In one embodiment, channel allocation and/orpolarization techniques may be applied in multiple-access wirelesscommunications architectures to provide selective, substantiallysimultaneous communications with wireless devices. In some embodiments,channels may be assigned to a plurality of transmitters to establishselective, substantially simultaneous wireless communications withdevices. In some embodiments, a transmitter is coupled to an antennaconfigured to provide selective, substantially simultaneouscommunications with wireless devices located in different spatial areas.In some embodiments, communications between wireless devices within asingle sector, between wireless devices in different sectors and betweenwireless devices and a wired network or wireless backhaul network may beprovided. As used herein, the term “sector” refers to a portion orsection of a spatial area in which wireless communications may beestablished. In one embodiment, the wireless communications architectureincludes a wireless device that allocates channels to sectors toincrease capacity and reliability of a wireless communication system.

In one embodiment, the wireless communications architecture comprises afrequency channel allocation technique that can enable reducedinterference in a wireless LAN. In one embodiment, the wireless LANemploys the IEEE 802.11 protocol. In one embodiment, the wireless LAN issectorized or apportioned into six (6) unique sector-ordered channelsets that provide reduced sector-to-sector interference for typicalantenna radiation patterns. In one embodiment, polarization techniquesmay be used to reduce sector-to-sector interference. Two sector-orderedcross-polarization schemes provide reduced interference in one exampleembodiment.

In one embodiment, a method for determining an assignment of wirelesscommunications channels to a plurality of wireless communicationstransmitter is provided. The method includes determining a plurality ofavailable wireless communications channels. The wireless communicationschannels may be determined in a frequency band or bands of interest.Determining a plurality of wireless communications channel assignmentsbased upon the plurality of available wireless communications channelsand a number of wireless communications transmitters in the plurality ofwireless transmitters is also included in the method. The method furtherincludes selecting from the plurality of wireless communications channelassignments, a particular wireless communications channel assignmentthat provides less interference relative to other wirelesscommunications channel assignments in the plurality of wirelesscommunications channel assignments. In one embodiment, the devicechooses number of channels to allocate to the given sectors such as toincrease capacity and reliability of a wireless communication system.

In one embodiment, available wireless communications channels may bedetermined from frequencies in a band of interest, such as withoutlimitation a frequency band selected to work with one of the IEEE802.11(a), (b), (g), the 802.15(x), 802.16(x) and 802.20(x) wirelesscommunications specifications, for example. Some embodiments will usefrequency bands other than the frequency bands specified by thesewireless communications standards.

In one embodiment, the method includes determining a power for eachwireless communications channel assignment. In one embodiment, the stepof selecting from the plurality of wireless communications channelassignments, a particular wireless communications channel assignmentthat provides less interference relative to other wirelesscommunications channel assignments in the plurality of wirelesscommunications channel assignments includes selecting from the pluralityof wireless communications channel assignments, a particular wirelesscommunications channel assignment that provides less interferencerelative to other wireless communications channel assignments in theplurality of wireless communications channel assignments and satisfies apower criteria for each of the plurality of wireless communicationschannel assignments. Power criteria such as without limitation exceedinga specified threshold, providing a greatest power relative to otherwireless communications channel assignments, and the like may be used.

In one embodiment, the method includes determining a channel separationfor each of the plurality of wireless communications channelassignments. In one embodiment, the step of selecting from the pluralityof wireless communications channel assignments, a particular wirelesscommunications channel assignment that provides less interferencerelative to other wireless communications channel assignments in theplurality of wireless communications channel assignments includesselecting from the plurality of wireless communications channelassignments, a particular wireless communications channel assignmentthat provides less interference relative to other wirelesscommunications channel assignments in the plurality of wirelesscommunications channel assignments and satisfies a channel separationcriteria for each of the plurality of wireless communications channelassignments. Separation criteria such as without limitation a minimumseparation between channels assigned to adjacent transmitters, minimumchannel separation between channels assigned to adjacent spatial regionsin which wireless communications is conducted and the like may be used.

In one embodiment, selecting from a plurality of wireless communicationschannel assignments a particular wireless communications channelassignment that provides less interference relative to other wirelesscommunications channel assignments in the plurality of wirelesscommunications channel assignments includes determining a reducedinterference cost.

In another aspect, one embodiment provides a method for determining anassignment of wireless communications channels to a plurality ofwireless communications transmitters. The method comprises determiningavailable wireless communications channels, which in one embodiment,includes selecting a first plurality of sets of wireless communicationschannels from a band of wireless communications frequencies; determininga power for each set of the first plurality of sets of wirelesscommunications channels; ordering the first plurality of sets ofwireless communications channels by power to form an ordered pluralityof sets of wireless communications channels; and selecting from theordered plurality of sets of wireless communications channels, sets ofwireless communications channels that satisfy a power criteria to form asecond plurality of sets of wireless communications channels. The methodfurther includes determining channel to transmitter assignments, whichin one embodiment, includes for each set of the second plurality of setsof wireless communications channels, determining each possibleassignment of channels in the set to transmitters; for each possibleassignment of channels in the set to transmitters, determining aseparation between the channels; for each possible assignment ofchannels in the set to transmitters, determining whether the separationsatisfies a specified separation criteria; and adding possibleassignment of channels in the set to transmitters to a plurality ofcandidate channel to transmitter assignments, if the possible assignmentof channels in the set to transmitters satisfies the specifiedseparation criteria. The method also includes selecting a channel totransmitter assignment, which in one embodiment includes determining anoverall interference generated by each one of the plurality of candidatechannel to transmitter assignments and choosing a candidate channel totransmitter assignment that reduces the overall interference.

In one embodiment, providing adjacent transmitters or sectors withopposite polarization enables reduction of adjacent transmitter/sectorinterference. In one embodiment, wireless communications transmittersare arranged according to a circular arrangement and adjacent wirelesscommunications transmitters are polarized according to a particularscheme. In one embodiment, sectors are arranged according to a circulararrangement and adjacent sectors are polarized according to a particularscheme. Example polarization schemes used in some embodiments include,but are not limited to, a cyclic rotation scheme, a reverse indexingscheme or a cyclic rotation and reverse indexing scheme. In oneembodiment, wireless communications transmitters are grouped into groupsand each the groups are provided with opposite polarization. In oneembodiment, wireless communications transmitters within each group havecongruent polarization. In one embodiment, sectors are grouped intosector groups and adjacent sector groups are provided with oppositepolarization. In one embodiment, sectors within each sector groupinghave congruent polarization. In one embodiment, the device determinesthat a channel or set of channels is allocated to other access points inthe vicinity and avoids using that channel or set of channels such as toavoid interfering with those access points.

In other aspects, the invention encompasses a computer apparatus and acomputer-readable medium configured to carry out the foregoing steps.

In another aspect, the present invention provides in one embodiment, awireless access point. The wireless access point may include an antennaconfigured to send and receive communications signals on a firstcommunications channel within a first section of a spatial area on afirst frequency and to send and receive communications signals on asecond communications channel within a second section of the spatialarea on a second frequency. The wireless access point may furtherinclude a management mechanism configured to assign the first and secondfrequencies to the first and second spatial areas in accordance with achannel sector assignment determined from a set of potential channel tosector assignments for available channels by selecting one of thechannel to sector assignments having a lower overall interferencerelative to other channel to sector assignments.

In one embodiment, the management mechanism of the wireless access pointis further configured to assign varying polarization to each of thefirst and second sections, thereby enabling reduced interference betweenthe first section and the second section.

In one embodiment the backhaul link is chosen first and then the channelallocation is determined for the sectors such as to ensure adequateperformance of the distribution network.

In some embodiments, the wireless communications architecture generallyincludes two or more wireless antenna arrangements that are eachconfigured to provide communications with wireless devices located in aparticular sector. Each wireless antenna arrangement is furtherconfigured to determine whether signals are being communicated on acommunications channel before transmitting on the communicationschannel. This may be implemented, for example, using a carrier sense orenergy detection mechanism. Wireless devices within a sector maycommunicate on the same or different communications channels, dependingupon the particular multiple access protocol employed. For example, TDMAor CSMA may be used to allow wireless devices in a sector to sharecommunications channels. Communications channels may also be usedsimultaneously in different sectors by different wireless devices.

Some embodiments may assign frequencies to transmitters and/or sectorsin accordance with a computational channel to sector assignmentdetermined to provide reduced interference. Some embodiments may provideimproved communications channel isolation using cross-polarizingtechniques. Some embodiments employing interference reduction techniquesmay achieve increases in aggregate data rate for a sectored deploymentand/or increases in the range for each sector. Some embodiments mayprovide the ability to set the number of independent channels on asectorized access point. Some embodiments may provide for allocatingchannels to sectors such as to avoid or stop interfering with accesspoints and to avoid interference from other noise source.

II. Operational Overview

FIG. 1A is a block diagram of a wireless communications apparatus 100configured in accordance with an embodiment of the invention. Apparatus100 is configured to allow selective communications with wirelessdevices located in sectors identified by reference numerals 102, 104,106, 108, 110 and 112. As depicted in FIG. 1A, each sector 102-112includes one or more wireless devices. For example, sector 102 includesfour wireless devices identified generally by reference numeral 114.

According to one embodiment of the invention, each sector 102-112 is aportion or section of a spatial area around apparatus 100. Each sector102-112 may be defined by a specified angle with respect to apparatus100. For example, sector 106 is an area defined by an angle a1, withrespect to apparatus 100. Sectors 102-112 may be defined by the sameangle, or different angles. In the present example, sectors 102-112 areeach defined by an angle of sixty degrees. Each sector 102-112 may alsobe defined by radius with respect to apparatus 100.

Apparatus 100 is configured to allow selective communications withwireless devices in any number of sectors and the sectors do not need tobe contiguous or provide complete coverage around apparatus 100. Thenumber, location and size of sectors 102-112 may be selected based upona wide variety of configuration criteria, depending upon therequirements of a particular implementation. Also, the size of sectors102-112 may be the same, or vary, depending upon the requirements of aparticular implementation. Example configuration criteria include,without limitation, the expected numbers and locations of wirelessdevices and physical constraints of a particular implementation. Forexample, when implemented in a building to provide wireless access to anetwork, the number and locations of wireless devices that will requirewireless access to the network may be considered. Also, the locations ofwalls and other physical obstacles, as well as the locations of noisesources and other wireless access apparatus may also be considered. Inoutdoor applications, the types and locations of natural obstacles aswell as buildings and other interference sources may be considered.

FIGS. 1B-1D depict example configurations for apparatus 100 to allowselective communications with wireless devices located in differentsectors. Specifically, FIG. 1B is a block diagram of apparatus 100configured to allow selective communications with wireless deviceslocated in three sectors 102-106. FIG. 1C is a block diagram ofapparatus 100 also configured to allow selective communications withwireless devices located in three sectors 102-106. In FIG. 1C, however,sectors 102-106 are located on one side of apparatus 100. Thisconfiguration may be used, for example, in situations where coverage isonly desired in sectors 102-106 as depicted in FIG. 1C. One examplesituation is where apparatus 100 is physically located within a buildingin a location where wireless devices will only be located in sectors102-106 as depicted in FIG. 1C with respect to apparatus 100. FIG. 1D isa block diagram of apparatus 100 configured to allow selectivecommunications with wireless devices located in two sectors 102, 104,but not in sectors 106, 108. Sectors 102, 104 are generallyangular-shaped areas defined by angles a1 and a2, respectively. Thisconfiguration may be used, for example, in situations where it is knownthat wireless devices are to be located in sectors 102, 104, but not insectors 106, 108. As depicted in FIG. 1D, apparatus 100 may beconfigured to allow selective communications in any number of sectors,of varying sizes and locations.

Wireless communications environments often change over time. Changes maybe attributable to the introduction of new noise sources or to mobilewireless devices changing locations over time. For example, in FIG. 1A,suppose that a mobile wireless device 116 moves from sector 108 tosector 110. As described in more detail hereinafter, apparatus 100 isconfigured to automatically detect that the move has occurred and tore-assign mobile wireless device 116 from sector 108 to 110 and performany required updates of configuration data and data structuresmaintained by apparatus 100. A frequency or timeslot assigned the mobilewireless device 116 may also be changed, depending upon the requirementsof a particular application. In CSMA applications, this may not berequired, since mobile wireless device 116 will automatically sense whenit can begin communicating in sector 110.

According to one embodiment of the invention, the configuration ofapparatus 100 may be dynamically changed over time to change one or moreattributes of sectors 102-112. This may include, for example, increasingor decreasing the number of sectors and/or changing the size or shape ofexisting sectors. The configuration of apparatus 100 may be changed forany reason. For example, apparatus 100 may be moved to a differentphysical location, where it is desirable to change the location or sizeof the sectors to provide better coverage. As another example, wirelessdevices may move to different locations over time.

FIG. 1E is a block diagram similar to FIG. 1D, except that a wirelessdevice 116 has moved from sector 104 to sector 106. Since apparatus 100is not configured to allow wireless communications in sector 106,wireless device 116 no longer has wireless communications supported byapparatus 100. As depicted in FIG. 1F, the configuration of apparatus100 is dynamically changed to expand sector 104 to provide wirelesscommunications for wireless device 116. The angle of sector 104 has beenchanged from a2, as depicted in FIG. 1E, to a3, as depicted in FIG. 1F.

Sectors may be dynamically changed to address other conditions, forexample for load balancing purposes. In this situation, the size (angle)of sectors are changed to increase or decrease the number of wirelessdevices in particular sectors to provide better load balancing, therebyincreasing throughput. Sectors may also be sub-divided into multiplesub-sectors, to further reduce the number wireless devices in anyparticular sub-sector. Sectors may also be overlapped, for example usingdifferent communications channels, to reduce the number of wirelessdevices operating on any particular communications channel.

The aforementioned reconfiguration of apparatus 100 may be performedusing a variety of techniques, depending upon the requirements of aparticular implementation. For example, the physical configuration ofone or more antenna elements may be changed to change the size or shapeof corresponding sectors. Changing the physical configuration of anantenna element may include several things, such as moving orre-orienting the antenna element, making physical adjustments to orre-sizing the antenna element, or even exchanging the antenna elementwith a different antenna element.

Instead of changing the physical configuration of an antenna element,the reconfiguration of apparatus 100 may be done by changing theelectrical configuration of the apparatus 100 to change the associatedsectors, for example using a beam forming network. The beam formingnetwork may be configured to vary the amplitude and relative phase oneach beam forming element to change the attributes of the beam, e.g., tocreate narrow or wide beams and to change the direction of the beams.Varactors may be used for this purpose. A point coordinator function ora distributed coordinator function may be used.

Instead of changing the physical configuration of an antenna element,the reconfiguration of apparatus 100 may be done by changing theelectrical configuration of the apparatus 100 to change the associatedsectors, for example by allocating the same channel frequency toadjacent sectors. This may be performed by either a power dividingnetwork at the radio frequency level or utilizing a protocol such asCSMA or other point coordination function at the software level.

III. Wireless Communications Apparatus

FIG. 2 is a block diagram that depicts a wireless communicationsapparatus 200 configured in accordance with an embodiment of theinvention. Apparatus 200 includes an antenna system 202, a RadioFrequency (RF) and bandpass filter network 204, a Wireless Local AreaNetwork (WLAN) Network Interface Card (NIC) network 206 or silicon thatperforms the function of the multiplicity of WLAN transceivers, a switchfabric 208 and a manager 210.

According to one embodiment of the invention, the antenna systemtransmits and receives electromagnetic radiation in a particular spatialdirection. The antenna system has the property that the radiation ittransmits and receives other than from the desired spatial location isminimized.

According to one embodiment of the invention, the antenna system hasmultiple transmit and receive antennas in any sector. The wirelesscommunication system has the property that it transmits and receivesradiation from any one of the radiating elements. The communicationsystem chooses which radiating element to transmit or receive in aparticular sector to maximize performance. The capability to havemultiple antennas in a sector provides diversity. There are many formsof diversity that can be implemented. For example, in one embodiment, anMRC diversity technique is employed where the output of the antennas arecombined in an optimal manner. In another embodiment, a switch diversitytechnique is employed where the antenna with the strongest signal isoutput to the baseband receiver.

According to one embodiment of the invention, RF and bandpass filternetwork 204 is configured to perform two functions. First, RF andbandpass filter network 204 is configured to perform band separation andseparate out one or more frequency bands from the RF signals provided byantenna system 202. For example, this may involve processing the RFsignal from antenna system 202 to obtain 2.4 and 5 GHz signals. Second,RF and bandpass filter network 204 is configured to performchannelization within each frequency band to improve system performance.The output of RF and bandpass filter network 204 is provided to WLAN NICnetwork 206.

RF and bandpass filter network 204 may include a beamforming pointingnetwork to dynamically change the angles of sectors 102-112. Thisfunction allows the size and/or location of sectors 102-112 to bedynamically changed.

According to one embodiment of the invention, RF and bandpass filternetwork 204 is configured to join multiple sectors 102-112. Thisincludes allowing a signal to be transmitted to or received frommultiple sectors 102-112 simultaneously. This may be useful, forexample, for increasing range in low isolation antenna systems at theexpense of throughput.

According to another embodiment of the invention, RF and bandpass filternetwork 204 may be omitted and protocol software may provide theappearance of joint multiple sectors 102-112. This includes allowing asignal to be transmitted to or received from multiple sectors 102-112simultaneously.

WLAN NIC network 206 is configured generally to change RF signals fromRF and bandpass filter network 204 into digital signals in the form ofdata packets. According to one embodiment of the invention, WLAN NICnetwork 206 is configured to amplify the RF energy before performingfrequency translation of the signal to base band separating the signalinto its in-phase and quadrature components. The respective componentsof the signal are sampled and demodulated into their constituent bits asspecified by an applicable standard, for example, the IEEE 802.11standard. The WLAN NIC network 206 may also be configured to providede-scrambling, error correction and low-level protocol functions, forexample, RTS/CTS generation and acknowledgment, fragmentation andde-fragmentation, and automatic beacon monitoring. The decoded bits aregrouped into packets, for example as specified by the IEEE standard, andthen provided to switch fabric 208 and manager 210.

Switch fabric 208 is coupled between WLAN NIC network 206 and a network212, such as a Local Area Network (LAN), Wide Area Network (WAN) or theInternet, and/or to a wireless backhaul system 214. Wireless backhaulsystem 214 may include a WLAN backhaul NIC and a WLAN backhaul radiatingelement that are not depicted in FIG. 2 for simplicity.

Manager 210 is configured to perform a variety of management and controlfunctions in apparatus 200. The particular functions performed bymanager 210 may vary, depending upon the requirements of a particularapplication, and the invention is not limited to manager 210 performingany particular tasks. Example management and control functions include,without limitation, managing overall system and sector configuration,managing the frequency bands, communications channels and communicationsprotocols for each sector, managing security protocols, managing thetransmit power level and receive sensitivity for each sector, detectingand alerting network administrators the presence of non-authorized orinterfering access points and managing communications between wirelessdevices and between wireless devices and network 212 and wirelessbackhaul system 214. Each of these management functions is described inmore detail hereinafter.

According to one embodiment of the invention, manager 210 is configuredto control switch fabric 208 to provide for the selective exchange ofdata between wireless devices in any particular sector 102-112 and alsobetween wireless devices in different sectors 102-112. Manager 210 isalso configured to perform switching functions to provide for theselective exchange of data between sectors 102-112 and network 212 andbetween sectors 102-112 and a wireless network connected to wirelessbackhaul system 214.

According to one embodiment of the invention, manager 210 is alsoconfigured to aggregate data from multiple wireless devices in one ormore sectors, and cause the aggregated data to be transmitted ontonetwork 212 or the wireless network connected to wireless backhaulsystem 214. For example, in FIG. 1A, manager 210 is configured toaggregate data from sectors 102-110 and transmit the aggregated dataonto network 212 or to wireless network via wireless backhaul system214. According to one embodiment of the invention, manager 210 transmitsthe aggregated data onto network 212 or to wireless network via wirelessbackhaul system 214 via one or more ports. As described in more detailhereinafter, manager 210 is also configured to manage the communicationschannels used to communicate with wireless devices and to manage thetransmit power and receive sensitivities of each sector 102-112.

According to one embodiment of the invention, manager 210 is alsoconfigured to maintain configuration data that defines the configurationand operation of apparatus 100. The configuration data may be stored ona volatile storage, such as a RAM, or a non-volatile storage, such asone or more disks or in a database, depending upon the requirements of aparticular application. The configuration data may specify, for example,the configuration of the overall system and each sector, informationabout each wireless device, such as identification and device typeinformation as well as the sector location of each wireless device. Theconfiguration data may also specify a current set of selectedcommunications channels, the particular communications channels to beused in each sector and by each wireless device and the particularfrequency bands and communications protocols to be used in each sectorand/or by each wireless device. As another example, the configurationdata may specify a transmit power level and receive sensitivity for eachsector. Manager 210 is also configured to update the configurationinformation in response to various events.

According to one embodiment of the invention, manager 210 is configuredto manage the movement of wireless devices between sectors. This mayinclude, for example, re-assigning communications channels and timeslots and updating other information relating to the wireless devicesthat moved. Suppose that a particular wireless device moves from sector102 to sector 104. In this situation, manager 210 may assign a newcommunications channel to the particular wireless device, for example ifthe current communications channel of the particular wireless device isnot being used in sector 104. Manager 210 then updates the configurationinformation to reflect that the particular wireless device is nowlocated in sector 104 and that communications with the particularwireless device are now to be made using the new assigned communicationschannel.

Antenna system 202, RF and bandpass filter network 204, WLAN NIC network206, switch fabric 208, manager 210, network 212 and wireless backhaulsystem 214 are communicatively coupled by links 216, 218, 220, 222 and224, as depicted in FIG. 2. Links 216-224 may be implemented by anymedium or mechanism that provides for the exchange of data between theseelements. Examples of links 216-224 include, without limitation, anetwork such as a Local Area Network (LAN), Wide Area Network (WAN),Ethernet or the Internet, or one or more terrestrial, satellite orwireless links. A link 226 provides for the exchange of control signalsbetween manager 210 and antenna system 202, RF and bandpass filternetwork 204, WLAN NIC Network 206 and switch fabric 208.

FIG. 3A is a block diagram that depicts a wireless communicationsarchitecture 300 configured in accordance with another embodiment of theinvention. Architecture 300 includes antenna elements, examples of theseelements may be dipoles, patch elements 302 or other antenna systems,304 that are configured to transmit on two different frequency bands.Antenna element 302 is coupled to a bandpass filter (BPF) 306 that iscoupled to a wireless chipset 308. Antenna element 304 is coupled to aBPF 310 that is coupled to a wireless chipset 312. BPFs 306, 310 arecontrollable by BPF control inputs from a control apparatus, such asmanagement processor and switch fabric 208. Wireless chipsets 308, 312convert RF signals into digital signals that are provided on digitaldata outputs. The digital signals may be provided in the form of datapackets that are provided to and switched by management processor andswitch fabric 208.

FIG. 3B is a block diagram that depicts a wireless communicationsarchitecture 350 configured in accordance with another embodiment of theinvention. In architecture 350, a dual frequency or ultra widebandantenna element 352 is coupled to a power divider 354. Power divider 354is coupled to a BPF 356 that is coupled to a wireless chipset 358. Powerdivider 354 is also coupled to a BPF 360 that is coupled to a wirelesschipset 362. As in FIG. 3A, BPFs 356, 360 are controllable by BPFcontrol inputs from a control apparatus, such as manager 210. Also,wireless chipsets 358, 362 convert RF signals into digital signals thatare provided on digital data outputs. The digital signals may beprovided in the form of data packets that are provided to and switchedby manager 210.

Although depicted in FIGS. 3A and 3B as discrete components, BPFs 306,310 and 356, 360 and wireless chipsets 308, 312 and 358, 362 may beintegrated into a single component. Also, BPFs 306, 310, 356, 360 maynot be used in some applications, at the expense of performance.

IV. Communications Channels, Protocols and Multiple Access Schemes

Any type of communications channel allocation scheme may be used withthe wireless communications architecture described herein. Theallocation of communications channels to sectors 102-112 may varydepending upon the requirements of a particular implementation and theinvention is not limited to any particular channel allocation scheme.Manager 210 is configured to manage the communications channels used tocommunicate with wireless devices. This may include, for example,determining initial communications channels to be used by wirelessdevices which may be based on isolation, interference or any otherfactor affecting performance, assigning communications channels andtimeslots to wireless devices and selecting communications protocols.This may also include periodically checking the performance of selectedcommunications channels and dynamically changing the communicationschannels used by wireless devices. This may include selecting a set ofcommunications channels to be used in each sector based uponcommunications channel performance.

As described in more detail hereinafter, apparatus 100 may be configuredto support multiple frequency bands operating simultaneously. Differentfrequency bands may be used in different sectors, or even in the samesector. For example, apparatus 100 may be configured with antennaelements and associated electronics to support communications on boththe 2.4 Ghz and 5 Ghz frequency bands. Apparatus 100 may also beconfigured to support any type and number of communications protocols.Example protocols supported by apparatus 100 include, withoutlimitations, the IEEE 802.11(x) communications protocols, such as802.11(a), (b), (g), the 802.15(x), 802.16(x) and 802.20(x)communications protocols, and other future communications protocols.

Apparatus 100 may also be configured to support any type and number ofmultiple access schemes to support communications with multiple wirelessdevices. For example, a Carrier Sense Multiple Access (CSMA), carrierdetect or energy detect scheme may be employed to allow multiplewireless devices to communicate using a specified set of communicationschannels. The wireless devices then communicate on the allocated set ofchannels using a multiple access scheme such as FDMA or TDMA.

V. Interference Mitigation and Power Control

Wireless communications apparatus 100 may be configured to reduce theamount of interference between wireless devices in different sectors102-112. It is extremely difficult, if not impossible, however tocompletely eliminate all interference between sectors because of thepresence of main and side lobes and near field coupling.

FIG. 4A illustrates a plurality of frequency channels according to the802.11b standard, which provides for 11 overlapping frequency channels401 in a frequency spectrum allocated for wireless communications in theUnited States. FIG. 4B illustrates one set of three channels chosen fromthe 11 channels, i.e., channel 1 412, channel 6 414 and channel 11 416,that are non-overlapping for the 2.4-2.5 GHz ISM band. Communications onthese channels will be non-interfering. The selection of non-overlappingchannels from a frequency band is not limited to the example of the802.11 frequency band illustrated by FIGS. 4A and 4B, rather, it isbroadly applicable to other frequency bands having finite allocation ofuseful channels in some embodiments of the present invention. In Japan,for example, 14 frequencies are presently allocated to wireless LANcommunications.

In a multi-sector wireless embodiment where the number of sectors isgreater than the total number of non-overlapping channels, use ofoverlapping channels may be desirable or necessary and thus thepotential for sector-to-sector frequency interference may increase.Antenna systems configured to provide multiple sector wirelesscommunications typically exhibit spill-over from a desired sector intoother sectors, which may frustrate attempts to provide absolute spatialdivision between wireless communications in different sectors. Forsituations were the sectors exceed number of non-overlapped channels,this spill-over, combined with channel overlap, may result ininterference which can reduce the overall performance of a deployment,in terms of aggregate throughput and/or in-sector range.

FIG. 5 illustrates an example of an antenna radiation pattern in anembodiment of the present invention. The radiation pattern for arealizable directional antenna as depicted by FIG. 5 includes a mainlobe502 and sidelobes 504. The main lobe may be defined by a half-power (−3dB) point, in which case FIG. 5 represents a pattern with a 60° beamwidth. In FIG. 5, three 60° sectors are shown. A first sector 510comprises a main sector. A second sector 512 experiences mainlobespillover 502, while a third sector 514 experiences sidelobe spill-over504.

In general, it is desirable to reduce the amount of interference betweensectors 510, 512 and 514 to below a specified level in order to providereliable performance and an acceptable level of quality of service. Forexample, according to one embodiment of the invention, varioustechniques are employed to reduce the magnitude of side lobes generatedby each sector to reduce the likelihood that transmissions from onesector will trigger a carrier or energy detection algorithm of anothersector. Reducing the amount of interference between sectors may alsoallow the same communications channels to be re-used, i.e., usedsimultaneously in more than one sector. This greatly increases thenumber of wireless devices that can be supported by apparatus 100 givena limited amount of available frequency spectrum.

In some embodiments, one or more of frequency division and polarizationdivision may be used to reduce sector-to-sector interference. As shownby FIG. 5, adjacent sectors, i.e., sectors 510 and 512 for example,experience the least spatial division, and therefore require the mostchannel separation (frequency division) and/or polarization separation.

Apparatus 100 may be configured to avoid other access points in itsvicinity as well as wireless devices in different sectors. Apparatus 100may be configured to reduce interference between wireless devices indifferent sectors using techniques described herein with reference toexample embodiments. For example, as described hereinafter in moredetail, one or more antenna elements may be physically configured toreduce interference between wireless devices in different sectors. Thismay include selecting materials and physically constructing antennaelements in a manner to reduce interference between sectors. Also, thepolarization of one or more antenna elements may be changed to reducethe amount of interference between wireless devices in differentsectors. For example, the polarization orientation of adjacent sectors102-112 may be varied to reduce interference between wireless devicesoperating in adjacent sectors 102-112. For example, an antenna elementthat provides communications with wireless devices in sector 102 mayhave a first polarization orientation. An antenna element that providescommunications with wireless devices in sector 104 may have a secondpolarization orientation, that is oriented at some angle to the first.In one embodiment, this may be ninety degrees with respect to theantenna element for sector 102.

According to one embodiment of the invention, frequency channelizationtechniques may be employed to select communications channels to reduceinterference between sectors and to provide a specified level of qualityof service. For example, as described above with reference to FIGS. 4Aand 4B, the IEEE 802.11(b) protocol specifies communications on elevencommunications channels, of which three (channels 1, 6, 11) arenon-overlapping. Thus, in one embodiment employing a three-sectorconfiguration, manager 210 may specify that communication channels 1, 6and 11 are to be used for the sectors 510, 512 and 514, respectively, toreduce the amount of interference and provide more favorable quality ofservice.

In one embodiment, a method of allocating channels to transmittersand/or sectors to minimize interference is provided. While the methodwill be described with reference to an example in which channels areassigned to sectors, the method is also applicable in embodiments inwhich channels are assigned to transmitters.

Let Ψ={C₁, . . . , C_(m)}denote the set of m available channels in theband of interest. Let S_(j) denote the jth subset of Ψ, i.e. S_(j) ⊂Ψ.For example, in an embodiment employing 802.11b, under a present FCCregulatory domain there are eleven channels, numbered from 1 to 11,ranging from 2.401 GHz to 2.467 GHz. Further, let S^(i) _(j) denote theith element of the set S_(j) and on the set S_(j) we define theoperation of subtraction between any two elements of this set. For anyset S_(j) the power of the set may be defined as:

$\begin{matrix}{{P\left( S_{j} \right)} = {\min\limits_{{i = {1\mspace{11mu} \ldots \mspace{14mu} n}}{k = {1\mspace{11mu} \ldots \mspace{14mu} n}}{i \neq k}}{{S_{j}^{i} - {S_{j}^{k}.}}}}} & (1)\end{matrix}$

The power of the set determines the channel separation between the twoclosest channels that belong to a set.

Let S _(k,i) define a transmitter or sector assignment i for the channelset S_(k). The quantity S _(k,i) corresponds to an ordered set of theelements of the set S_(k) where the first element of the arraycorresponds to sector 1 (or transmitter 1) and the nth elementcorresponds to the nth sector (or transmitter). The tilde is used todistinguish between the two sets where the set S _(k,i) is the ithordered set meaning that the relation of the channels in the setcorresponds to their respective sector (or transmitter) assignments.

If the set S_(k) is comprised of three elements S_(k)={C₁, C₂, C₃}, forexample, then the possible ordered channel sets are:

S _(k,1)={C₁C₂C₃}

S _(k,2)={C₁C₃C₂}

S _(k,3)={C₂C₁C₃}

S _(k,4)={C₂C₃C₁}

S _(k,5)={C₃C₁C₂}

S _(k,6)={C₃C₂C₁}  (2)

In these ordered channel sets, differences in the sequence of channelscorrespond to different channel to sector (or transmitter) assignments.In the illustrated example embodiment, the ordered channel sets S _(k,1)and S _(k,2) are distinct sets because the channels in each set are havea different ordering even though the two sets have exactly the samechannels.

The separation distance of the set S _(k,i) for circular antenna systemmay be defined as:

$\begin{matrix}{{S\left( {\overset{\_}{S}}_{k,i} \right)} = {\min\limits_{r = {1\; \ldots \mspace{14mu} n}}{{{\overset{\_}{S}}_{k,i}^{r} - {\overset{\_}{S}}_{k,i}^{r + {1{mod}\; n}}}}}} & (3)\end{matrix}$

For a linear system, the separation distance may be defined as:

$\begin{matrix}{\; {{S\left( {\overset{\_}{S}}_{k,i} \right)} = {\min\limits_{{r = 1},\mspace{11mu} {\ldots \mspace{14mu} n}}{{{\overset{\_}{S}}_{k,i}^{r} - {\overset{\_}{S}}_{k,i}^{r + 1}}}}}} & (4)\end{matrix}$

The measures in equations (3) and (4) determine the separation betweenadjacent sectors (or transmitters). This may be performed whendetermining how close the assigned channels are to channels assigned toadjacent sectors (or transmitters). In some embodiments, thisdetermination can enable reduced interference.

In one embodiment, an interference function may be defined as:

$\begin{matrix}{{g\left( {\theta,{\overset{\_}{S}}_{k,i}} \right)} = {\sum\limits_{r = 1}^{n}\; {\sum\limits_{t = r}^{n}\; {w^{rt}\left( {\theta,{\overset{\_}{S}}_{k,i}^{r},{\overset{\_}{S}}_{k,i}^{t}} \right)}}}} & (5)\end{matrix}$

Where the interference generated as a function of angular position andchannel selection is given by:

w^(n)(θ, S ^(r) _(k,i), S ^(t) _(k,i))≧0 ∀0≦θ<2π, { S ^(r) _(k,i), S^(t) _(k,i)}∈Ψ  (6)

Equation 6 represents a cost that is arbitrary and encompasses the classof all interference generating functions.

An example of the interference generating function, in one embodiment,is defined as:

$\begin{matrix}{{{w^{rt}\left( {\theta,{\overset{\_}{S}}_{k,i}^{r},{\overset{\_}{S}}_{k,i}^{t}} \right)} = {\int_{f_{r}^{l}}^{f_{r}^{u}}{{A\left( {{\theta - \theta_{r}},f} \right)}{r\left( {{\overset{\_}{S}}_{k,i}^{r},{\overset{\_}{S}}_{k,i}^{t},f} \right)}{n\left( {{\overset{\_}{S}}_{k,i}^{r},{\overset{\_}{S}}_{k,i}^{t},f} \right)}\ {f}}}}{0 \leq \theta_{r}^{L} \leq \theta \leq \theta_{r}^{U} < {2\; \pi}}} & (7)\end{matrix}$

Where f_(r) ^(L), and f_(r) ^(U) are the lower and upper frequencies ofchannel r. The quantities θ_(r) ^(L) and θ_(r) ^(U) are the lower andupper angular frequencies of r. The quantity A(θ, f) is the antennaradiation pattern as a function of angular position and frequency andthe quantities r( S _(k,i) ^(r), S _(k,i) ^(t), f) and n( S _(k,i) ^(r),S _(k,i) ^(t), f) represent the channel overlap as a function of channelnumber and frequency and the antenna near field and reflectioninterference generated.

Some examples of interference cost functions that can be used tominimize the interference in some embodiments are:

$\begin{matrix}{M = {\min\limits_{0 \leq \theta < {2\; \pi}}{g\left( {\theta,{\overset{\_}{S}}_{k,i}} \right)}}} & (8) \\{M = {\int_{0}^{2\; \pi}{g\ \left( {\theta,{\overset{\_}{S}}_{k,i}} \right)}}} & (9)\end{matrix}$

FIG. 6A is a flowchart depicting an example of allocating channels inaccordance with an embodiment of the invention. In block 601, availablewireless communications channels are determined for a band of wirelesscommunications frequencies of interest, as depicted in further detail inFIG. 6B. For example, if the band of interest is the IEEE 802.11frequency band illustrated in FIG. 4A, then channels 1-11 are availablechannels. In other embodiments, many other frequency bands of interestmay be selected. In block 602, channel to transmitter assignments aredetermined, as depicted in further detail in FIG. 6C. In someembodiments, channel to transmitter assignments may comprise assigningchannels to individual radio transmitters. In alternative embodiments,channel to transmitter assignments may comprise an assignment ofchannels to sectors serviced by a sectorized antenna. In one embodiment,channel to transmitter assignment may be performed according to anoverlap criteria that may specify, for example, a minimum separation forchannels assigned to adjacent transmitters or sectors. For example, inone embodiment, a minimum of two channels can be required to separate afirst channel and a second channel assigned to adjacent transmitters. Inanother embodiment, a criteria such as each sector must be at least nchannels away from the other sectors may be used. The channelseparation, r, may be chosen as a function of the number of utilizedtransmitters or sectors. The channel separation, r, is applicationspecific and may depend on the available transmitters or sectors whichare to be used. In block 603, a channel to transmitter assignment isselected, as depicted in further detail in FIG. 6D.

In one embodiment, a channel to transmitter assignment that minimizesoverall interference is selected from among candidate channel totransmitter assignments. In other embodiments, a channel to transmitterassignment that provides any one or a combination of criteria, such asfor example without limitation: a) maximal power, b) greatest range, c)increased throughput of the device, d) increased network throughput, e)minimal disruption to network already in place, f) avoidance of otherprovisioned services, g) minimal packet error rate (PER) or bit errorrate (BER), h) minimal channel utilization, i) minimal channel blockingprobabilities, j) greater number of stations to connect at the highestrates, k) adequate quality of service for station requiring highthroughput and/or low latency and/or low jitter, l) avoidance of radarsor other radiolocation devices, m) cognitive radio function based upon asense of the channels used to determine that other services or users arenot present, may be chosen. In one embodiment, the transmitter maymonitor the set up to ensure any of the above criteria are satisfied.

FIG. 6B is a flowchart depicting an example of determining the availableset of channels in accordance with an embodiment of the invention. Inone embodiment, sets of available channels which correspond to thelargest frequency separation are determined based on the informationthat there are m channels and n of these are to be used in thesectorization scheme.

In block 611, from the set of m available channels {C₁, . . . , C_(m)} alist L={S₁, . . . , S_(k)}, of sets of channels is constructed. The listL can contain exactly n elements where m≧n. Since there are a possible mchannels, there are exactly

$\; {\begin{pmatrix}m \\n\end{pmatrix} = {\frac{m!}{{\left( {m - n} \right)!}{n!}}{sets}}}$

in the list in one example embodiment. In block 612, for all sets in thelist L, the power of each set is determined in accordance with equation(1). In block 613, list L is ordered based on the power of each set. Inblock 614, the sets having the largest power are chosen and a new listdenoted by {circumflex over (L)} is constructed. In various embodiments,sets may be chosen using one or more criteria, such as for examplewithout limitation: a) selecting a fixed number of sets which can beevaluated (tried and measurements made) in the available set up time, b)determining the score for every set, wherein each set is evaluated(tried), c) determining the score for every set and trying the first mwith the highest probability of success, d) determining the score of allsets and choosing the highest.

The list {circumflex over (L)} corresponds to the list of candidatechannel sets that will be tested to determine whether each of thecandidate channel sets meets a minimum separation criteria, for example.The list L corresponds to the channel sets that have the greatestchannel separation. In one embodiment, this process provides candidatechannels sets that are separated as far as possible in frequency to reside effects such as near field coupling.

FIG. 6C is a flowchart depicting an example of determining the channelassignments in accordance with one embodiment of the invention. In block621, minimum separation criteria for channels assigned to adjacenttransmitters or sectors is established. For example, in one embodiment,channels assigned to adjacent transmitters may be subjected to a minimumseparation criterion that specifies no channel overlap. In anotherexample embodiment, sectors serviced by a sectorized antenna may besubject to a criterion that specifies that at least two channelsseparate the channels assigned to the adjacent sectors. In otherembodiments, various other minimum separation criteria may be used. Inblock 622, for each candidate channel set in list {circumflex over (L)},possible channel to transmitter assignments are determined. For example,for each set S_(k) all n!possible permutations of the candidate channelset are determined, where a permutation is denoted by S _(k,i). In block623, for each permutation the separation of the set is determined. Forexample, S( S _(k,i)) is computed, and a determination is made whetherthe result satisfies the minimum separation criteria as specified inblock 621. If a channel set satisfies the minimum separation criteriathen the set is a candidate for utilization. Otherwise, the permutationis discarded and the next permutation is determined. In someembodiments, the foregoing process steps are completed for all possibleassignments of channel sets to transmitters or sectors.

FIG. 6D is a flowchart depicting an example of selecting a channelassignment in accordance with an embodiment of the invention. In block631, an overall interference generated by each channel to transmitterassignment is determined. In block 632, a candidate channel set thatminimizes the overall interference is chosen.

The foregoing processing will next be illustrated with reference to anexample in the context of a six-sector 802.11b system with elevenavailable channels numbered 1 to 11. The overlap criteria for channelselection to reduce interference in a 6-sector implementation are: (1)no sector is closer than 2 channels from any other sector; and (2)adjacent sectors are at least 4 channels apart, in other words,separation is greater than or equal to 4. Accordingly, the power of theset is equal to 2. (Power of a set is a mathematical concept that refersto how close two elements of a set are. For example consider the set{3,1,9,25,101}. The power of this set is 2 because the first element,number 3, and the second element, number 1, are two units away.)

Criterion (1) leads to the un-ordered 6-channel set {1, 3, 5, 7, 9, 11},while criterion 2 leads to the five, 6-channel sector-ordered sets asshown in Table 1.

TABLE 1 802.11b 6-Channel Sets for Reduced Interference {1, 5, 9, 3, 7,11} {1, 5, 9, 3, 11, 7} {1, 5, 11, 7, 3, 9} {1, 7, 3, 9, 5, 11} {1, 7,3, 11, 5, 9}

A cyclic rotation of a channel set and/or reverse indexing (with respectto sector number) also may meet the criteria. For example, FIG. 7illustrates variations of an example sector-ordered 6-channel set inaccordance with an embodiment of the invention. FIG. 7 shows the firstchannel set 701 from Table 1, along with a rotation 702, and a reversaland rotation 703 of the same channel set in accordance with oneembodiment.

Some embodiments may employ cross-polarization techniques to reducesector-to-sector interference. In FIG. 8, an example polarizationassignment is shown in one embodiment. In the following description, +1and −1 denote two different polarizations. In the case of linearpolarization, +1 (−1) may denote vertical polarization, in which case −1(+1) would denote horizontal polarization. For circular polarization, +1(−1) may denote right-circular polarization and −1 (+1) would denoteleft-circular polarization in some embodiments. As depicted in FIG. 8,one cross-polarization technique comprises providing adjacent sectorswith different polarizations to reduce interference between adjacentsectors. For example, in FIG. 8, sector 1 (801) is configured to operateon channel 5 with a +1 polarization. Adjacent sector 2 (802) isconfigured to operate on channel 9 with a (−1) polarization. A cyclicrotation of this polarization assignment (with respect to sector) wouldachieve the interference reduction in one embodiment. Techniques forcontrolling cross-polarization in one embodiment are described belowwith reference to FIG. 11A.

FIG. 9 illustrates another cross polarization assignment in accordancewith an embodiment of the invention. As depicted in FIG. 9, two 3-sectorhemispheres, a “front” hemisphere 902 and a “back” hemisphere 904 havechannel assignments such that no sectors within a hemisphere are closerthan four channels. In the illustrated embodiment, however,cross-hemisphere sectors can be as close as two channels. For example,as depicted by FIG. 9, sector three in front hemisphere 902 is usingchannel one and sector five in back hemisphere 904 is using channelthree. Sector three and sector five are separated by only one sector,sector 4, and channel one and channel three are within two channels ofone another. Because sector three, in front hemisphere 902 is polarizedwith +1 polarization, while sector five, in back hemisphere 904, ispolarized with −1 polarization, however, sector one and sector five canuse channel one and channel three without substantial interference. Inthe embodiment illustrated by FIG. 9, the polarization assignment issuch that all sectors in the front hemisphere 902 are cross-polarizedwith respect to the back hemisphere 904, however, sectors within ahemisphere have congruent polarization.

In situations where a communications protocol is employed that does notinclude non-overlapping channels, a testing scheme may be used toidentify an assignment of communications channels to achieve specifiedinterference and quality of service levels. This may include an initialtest to identify a set of initial communications channels to be assignedto the sectors, as well as subsequent periodic testing to provide anupdated set of communications channels.

According to one embodiment of the invention, transmit power levels andreceive sensitivities are selected to improve communications and reduceinterference between sectors. Transmit power levels and receivesensitivities may be selected on a per transmitter, a per sector, perwireless device, or even per packet basis, depending upon therequirements of a particular implementation. Varying the transmit powerlevel generally changes the size of a transmission area. For example, inFIG. 1G, the transmit power levels of apparatus 100 are selected tocause sector 102 to have a radius of R1 and sector 104 to have a radiusof R2. In this example, the wireless devices in sector 104 are locatedrelatively closer to apparatus 100 than the wireless devices in sector102. Thus, less power needs to be used with the antenna elementassociated with sector 104, relative to the antenna element associatedwith sector 102.

Selectively adjusting the transmit power for each sector serviced byapparatus 100 reduces the overall power consumed by apparatus 100,reduces the possible interference between sectors 102 and 104, andimproves security. Varying the receive sensitivity for a particularsector changes the general sensitivity to the particular sector totransmissions from other sectors and other types of interference.According to one embodiment of the invention, the receive sensitivityfor a sector is optimized to provide a specified quality of service forwireless devices in the sector, while reducing the likelihood ofinterference. The transmit power level and receive sensitivities may beadjusted together to optimize sector performance.

Transmit power levels and receive sensitivities may be dynamicallyadjusted over time to compensate for changing conditions. This mayinclude, for example, changes in the configuration of apparatus 100,changes in the locations and numbers of wireless devices, changes in thefrequency band or channels being used, changing power or quality ofservice requirements and changes in interference sources.

VI. Antenna Configurations

Various antenna configurations may be employed with the wirelesscommunications architecture described herein, depending upon therequirements of a particular application. FIG. 10A is a block diagramthat depicts a top view of an antenna apparatus 1000 used with antennasystem 202. Antenna apparatus 1000 includes various antenna elementsconfigured to provide wireless communications with wireless deviceslocated in sectors 1002-1012. Specifically, antenna apparatus 1000includes a center reflector portion 1014. With respect to sector 1002,antenna apparatus 1000 includes a radiating assembly 1016 configured toradiate electromagnetic energy into sector 1002. Antenna apparatus 1000also includes metal septums 1018, 1020 that are configured to definesector 1002. Metal septums 1018, 1020 may be separated from centerreflector portion 1014, as indicated by apertures 1022, 1024, to reducecoupling between sector 1002 and the other sectors 1004-1012. Accordingto one embodiment of the invention, septums 1018, 1020 are positionedfrom center reflector portion 1014 at a distance that is proportional tothe transmission wavelength. Antenna apparatus 1000 also includes RFchokes 1026, 1028, coupled to the ends of metal septums 1018, 1020.

Antenna apparatus 1000 may also include radio frequency absorptivematerial, such as foam or other material or photonic bandgap structures,disposed between the metal septums and the top and bottom of antennaapparatus 1000 to further reduce coupling between sectors. For example,FIG. 10B is a side view of antenna apparatus 1000 depicting the variouscomponents of FIG. 10A. As depicted in FIG. 10B, radio frequencyabsorptive material 1030 is disposed on top and bottom of septums 1018,1020 to reduce electromagnetic coupling between sectors 1002-1012.

Although antenna apparatus 1000 has been described in the context ofsector 1002, antenna apparatus 1000 includes similar antenna elementsfor the other sectors 1004-1012. The dimensions and characteristics ofthe other antenna elements that provide wireless communications forsectors 1004-1012 may be the same as or different from theaforementioned antenna elements that provide wireless communications forsector 1002.

FIG. 11A is a block diagram of an end view of a radiating assembly 1100configured in accordance with an embodiment of the invention. Radiatingassembly 1100 may be used for radiating assembly 1016 in antennaapparatus 1000. Radiating assembly 1100 includes a base 1102 and patchelements 1104, 1106 attached thereto. Patch elements 1104, 1106 may bebuilt upon a PCB such as FR4, or other dielectric substrate. Althoughradiating assembly 1100 is configured with two patch elements 1104,1106, radiating assembly 1100 may be configured with a single patchelement, depending upon the requirements of a particular implementation.Patch elements 1104, 1106 are oriented with respect to each other at anangle B, as depicted in FIG. 11A, to introduce polarization diversity.According to one embodiment of the invention, patch elements 1104, 1106are oriented at approximately ninety degrees with respect to each other,although other angles may be used, depending upon the requirements of aparticular application. Radiating assembly 1100 may also be orientedwith respect to other radiating assemblies in an antenna apparatus todecrease polarization alignment and provide greater isolation betweensectors. For example, radiating assembly 1016 for sector 1002 may beoriented with respect to the radiating assemblies for sectors 1004-1012to decrease polarization alignment and provide greater isolation betweensectors 1002 and 1004-1012.

FIG. 11B is a block diagram that depicts patch element 1104 configuredaccording to one embodiment of the invention. In this embodiment, patchelement 1104 is duel frequency and includes a radiating element 1108.Radiating element 1108 is generally “T” shaped and includes a longmicrostrip 1110 for low frequency operation and a short microstrip 1112for high frequency operation. Two microstrips 1110, 1112 are notrequired by the invention, and some implementations may have only asingle microstrip where communications in only single frequency band arerequired. As an alternative to using the “T” shaped radiating element1108 in dual-band applications, two separate patch elements may be used,where one of the patch elements is a small patch element that includes alow frequency microstrip and the other larger patch element includes ahigh frequency microstrip. In this situation, the smaller high frequencypatch element may be suspended above the larger lower frequency patchelement.

VII. Implementation Mechanisms, Alternatives & Extensions

The wireless communications architecture described herein may beimplemented in hardware, software, or any combination of hardware andsoftware. For example, manager 210 may be implemented using a genericcomputing platform that executes various software programs to performthe functions described herein.

FIG. 12 is a block diagram that illustrates an example computer system1200 upon which an embodiment of the invention may be implemented.Computer system 1200 includes a bus 1202 or other communicationmechanism for communicating information, and a processor 1204 coupledwith bus 1202 for processing information. Computer system 1200 alsoincludes a main memory 1206, such as a random access memory (RAM) orother dynamic storage device, coupled to bus 1202 for storinginformation and instructions to be executed by processor 1204. Mainmemory 1206 also may be used for storing temporary variables or otherintermediate information during execution of instructions to be executedby processor 1204. Computer system 1200 further includes a read onlymemory (ROM) 1208 or other static storage device coupled to bus 1202 forstoring static information and instructions for processor 1204. Astorage device 1210, such as a magnetic disk or optical disk, isprovided and coupled to bus 1202 for storing information andinstructions.

Computer system 1200 may be coupled via bus 1202 to a display 1212, suchas a cathode ray tube (CRT), for displaying information to a computeruser. An input device 1214, including alphanumeric and other keys, iscoupled to bus 1202 for communicating information and command selectionsto processor 1204. Another type of user input device is cursor control1216, such as a mouse, a trackball, or cursor direction keys forcommunicating direction information and command selections to processor1204 and for controlling cursor movement on display 1212. This inputdevice typically has two degrees of freedom in two axes, a first axis(e.g., x) and a second axis (e.g., y), that allows the device to specifypositions in a plane.

The invention is related to the use of computer system 1200 in awireless communications architecture. According to one embodiment of theinvention, wireless communications are provided by computer system 1200in response to processor 1204 executing one or more sequences of one ormore instructions contained in main memory 1206. Such instructions maybe read into main memory 1206 from another computer-readable medium,such as storage device 1210. Execution of the sequences of instructionscontained in main memory 1206 causes processor 1204 to perform theprocess steps described herein. One or more processors in amulti-processing arrangement may also be employed to execute thesequences of instructions contained in main memory 1206. In alternativeembodiments, hard-wired circuitry may be used in place of or incombination with software instructions to implement the invention. Thus,embodiments of the invention are not limited to any specific combinationof hardware circuitry and software.

The term “computer-readable medium” as used herein refers to any mediumthat participates in providing instructions to processor 1204 forexecution. Such a medium may take many forms, including but not limitedto, non-volatile media, volatile media, and transmission media.Non-volatile media includes, for example, optical or magnetic disks,such as storage device 1210. Volatile media includes dynamic memory,such as main memory 1206. Transmission media includes coaxial cables,copper wire and fiber optics, including the wires that comprise bus1202. Transmission media can also take the form of acoustic or lightwaves, such as those generated during radio wave and infrared datacommunications.

Common forms of computer-readable media include, for example, a floppydisk, a flexible disk, hard disk, magnetic tape, or any other magneticmedium, a CD-ROM, any other optical medium, punch cards, paper tape, anyother physical medium with patterns of holes, a RAM, a PROM, and EPROM,a FLASH-EPROM, any other memory chip or cartridge, a carrier wave asdescribed hereinafter, or any other medium from which a computer canread.

Various forms of computer readable media may be involved in carrying oneor more sequences of one or more instructions to processor 1204 forexecution. For example, the instructions may initially be carried on amagnetic disk of a remote computer. The remote computer can load theinstructions into its dynamic memory and send the instructions over atelephone line using a modem. A modem local to computer system 1200 canreceive the data on the telephone line and use an infrared transmitterto convert the data to an infrared signal. An infrared detector coupledto bus 1202 can receive the data carried in the infrared signal andplace the data on bus 1202. Bus 1202 carries the data to main memory1206, from which processor 1204 retrieves and executes the instructions.The instructions received by main memory 1206 may optionally be storedon storage device 1210 either before or after execution by processor1204.

Computer system 1200 also includes a communication interface 1218coupled to bus 1202. Communication interface 1218 provides a two-waydata communication coupling to a network link 1220 that is connected toa local network 1222. For example, communication interface 1218 may bean integrated services digital network (ISDN) card or a modem to providea data communication connection to a corresponding type of telephoneline. As another example, communication interface 1218 may be a localarea network (LAN) card to provide a data communication connection to acompatible LAN. Wireless links may also be implemented. In any suchimplementation, communication interface 1218 sends and receiveselectrical, electromagnetic or optical signals that carry digital datastreams representing various types of information.

Network link 1220 typically provides data communication through one ormore networks to other data devices. For example, network link 1220 mayprovide a connection through local network 1222 to a host computer 1224or to data equipment operated by an Internet Service Provider (ISP)1226. ISP 1226 in turn provides data communication services through theworldwide packet data communication network now commonly referred to asthe “Internet” 1228. Local network 1222 and Internet 1228 both useelectrical, electromagnetic or optical signals that carry digital datastreams. The signals through the various networks and the signals onnetwork link 1220 and through communication interface 1218, which carrythe digital data to and from computer system 1200, are example forms ofcarrier waves transporting the information.

Computer system 1200 can send messages and receive data, includingprogram code, through the network(s), network link 1220 andcommunication interface 1218. In the Internet example, a server 1230might transmit a requested code for an application program throughInternet 1228, ISP 1226, local network 1222 and communication interface1218. In accordance with the invention, one such downloaded applicationmanages a wireless communications architecture as described herein.

Processor 1204 may execute the code as it is received, and/or stored instorage device 1210, or other non-volatile storage for later execution.In this manner, computer system 1200 may obtain application code in theform of a carrier wave.

In the foregoing specification, embodiments of the invention have beendescribed with reference to numerous specific details that may vary fromimplementation to implementation. Thus, the sole and exclusive indicatorof what is, and is intended by the applicants to be, the invention isthe set of claims that issue from this application, in the specific formin which such claims issue, including any subsequent correction. Hence,no limitation, element, property, feature, advantage or attribute thatis not expressly recited in a claim should limit the scope of such claimin any way. The specification and drawings are, accordingly, to beregarded in an illustrative rather than a restrictive sense.

1. A wireless access point for providing wireless access to a wirednetwork within a building, the wireless access point comprising: a firstantenna arrangement configured to communicate with wireless deviceswithin a first section of a spatial area around the wireless accesspoint, wherein the first antenna arrangement is further configured todetermine whether a first communications channel assigned to the firstsection of the spatial area is currently being used to carrycommunication signals before transmitting any communication signals ontothe first communications channel; a second antenna arrangementconfigured to communicate with wireless devices within a second sectionof a spatial area around the wireless access point, wherein the secondantenna arrangement is further configured to determine whether a secondcommunications channel assigned to the second section of the spatialarea is currently being used to carry communication signals beforetransmitting any communication signals onto the second communicationschannel; and a management mechanism configured to manage the operationof the first and second antenna arrangements and to assign channels tothe first spatial area and the second spatial area according to aparticular wireless communications channel assignment selected from aplurality of wireless communications channel assignments, wherein theparticular wireless communications channel assignment provides lessinterference relative to other wireless communications channelassignments in the plurality of wireless communications channelassignments.
 2. A wireless access point, comprising: an antennaconfigured to send and receive communications signals on a firstcommunications channel within a first section of a spatial area on afirst frequency and to send and receive communications signals on asecond communications channel within a second section of the spatialarea on a second frequency; and a management mechanism configured toassign the first and second frequencies to the first and second spatialareas in accordance with a channel sector assignment determined from aset of potential channel to sector assignments for available channels byselecting one of the channel to sector assignments having a loweroverall interference relative to other channel to sector assignments. 3.The wireless access point as recited in claim 2, wherein the managementmechanism is further configured to assign varying polarization to eachof the first and second sectors, thereby enabling reduced interferencebetween the first sector and the second sector.
 4. A wirelesscommunications system comprising: a first antenna arrangement having afirst transceiver configured to transmit and receive communicationssignals on a communications channel within a first section of a spatialarea around the wireless communications apparatus; a second antennaarrangement having a second transceiver configured to transmit andreceive communications signals on the communications channel within asecond section of the spatial area around the wireless communicationsapparatus; and wherein frequencies are allocated to each of theplurality of sections in accordance with a channel to sector assignmentdetermined from a set of potential channel to sector assignments foravailable channels by selecting one of the channel to sector assignmentshaving a lower overall interference relative to other channel to sectorassignments.